Pressure regulating valves for pressure cookers already known consist essentially of a tubular projection extending from the center of the pressure cooker lid. A needle is positioned on the outwardly turned opening of the projection. This needle is part of a body arranged around the tubular projection and on which weights can be placed to regulate the working pressure inside the cooker. Steam escape openings also are provided.
In the oldest form of construction of this type of valve, as for example, in the D. K. Linde valve shown in U.S. Pat. No. 2,633,870 and others, the shape of the body constituted by the weights does not favor a perfect dynamic balance around the point on which the needle is poised. This is a reason why the valve does not have a satisfactory performance.
In view of solving this problem, the pressure regulating valve of this invention was developed, which consists essentially of a tubular projection protruding from the center of the cooker lid and having an outer opening on which a needle is positioned. The needle extends from the bottom inside surface of a piece formed as an inverted cup inserted around the tubular projection protruding from the lid. On the outside surface of said bottom a threaded projection is provided. Intermediate openings are provided for steam escaping, and around the downward turned aperture said inverted cup piece forms an external flange and another internal flange. The latter has a thread to be screwed on and off on a thread provided outside the free end of the tubular projection protruding from the lid, in order to insert or to remove the inverted cup piece, or to keep it lifted during the depressurizing operations. On the external flange and around the inverted cup piece are placed two outwardly hemispherical weights forming together a spherical body. The external threaded projection in the bottom of the inverted cup piece receives a weight fastening head.
The spherical shape of the valve body, in addition to distinguishing it from other valves, causes the body mass to be uniformly distributed around a supporting central point (needle) giving the whole a better dynamic balance and, consequently, a better performance.
In order to improve the spherical-shaped valve performance, a first improvement was introduced which consisted of providing the internal surface of the inverted cup-shaped piece with longitudinal channels aimed at directing downwardly part of the steam expelled from the circumferential passage defined between the needle and the external opening of the tubular projection extending from the lid which, together with the spherical shape of the valve body, gives the combination a better dynamic balance and, therefore, better valve performance.
Another drawback of many conventional valves is their having weights the same shape causing them to be used inadequately. The spherical shape of the valve body of this invention and the consequent hemispherical shape of its weights prevent inadequate use of same.
Many conventional pressure regulating valves have slanted and downwardly-turned steam escape opening, as well as relatively large one which can make their execution difficult. Those openings are liable to make a certain lack of precision in cutting, which makes it necessary to use some effort when displacing the whole vertically.
The steam escape openings in the pressure regulating valve of this invention are radically disposed, tending to prevent steam that is expelled through same from vertically displacing the valve body and making for easy execution at the manufacturing level.
The slanted and downwardly-turned position of the steam escape openings of the conventional valves are supposed to direct the steam downwards, keeping it from striking the user. Nevertheless, in many cases, part of the expelled steam hits the cooler lid surface, deviates its course, and is dispersed through an arc around the cooker in which it can strike the user.
The horizontal position of the escape openings of the valve of this invention might cause said dispersion through the are around the cooker. In order to avoid this, the escape openings in the inverted cup piece are at a level above the base of the bottom weight and the top weight is given a calotte-shape which, together with the bottom weight base and the outside surface of the inverted cup piece, defined a chamber destined to break the steam jet expelled into the environment through other escape openings provided in the second top calotte shaped weight.
During operation of the valve and as a result of the steam escaping from the interior of the cooker, upper and bottom weights continuously rotate around the inverted cup-shaped body. At some moments only of said rotation, openings provided in the calotte-shaped weight coincide with openings of the inverted cup-shaped body, causing the steam to escape outwardly. During most of the calotte-shaped weight rotation, its openings do not coincide with openings of said inverted cup-shaped body, i.e., they coincide with the inner walls of the upper weight. As a result of such coincidence, steam jets coming from the openings of the inverted cup-shaped body are broken by said walls, thereby reducing their outlet pressure. Thus, because of said difference in phase between openings of said inverted cup-shaped body and openings of said calotte-shaped weight, a continuous breaking of the steam jet is achieved.
Another feature of conventional pressure regulating valves is that a large number of them have the weights fixed on the support through the threading on the weights themselves, or else through pieces destined to fix them on a whole. This prevents and/or makes it difficult to handle the whole during the weight changing operation, especially when the cooker is being used.
With a view to solve the problem, the pressure regulating valve for pressure cookers of this invention has its weights fixed by projections provided in the top head which, when aligned or misaligned in relation to longitudinal grooves provided in the weight openings coupled to the inverted cup piece, allow for the removal or for the positioning of weights, as well as for their fixation on the whole.
In other words, projections provided in the upper head when aligned in relation to the longitudinal grooves provided in the weights, allow for the positioning and for the removal of said top and bottom weights around the inverted cup-shaped body.
However, upon positioning of the weights and as a result of the valve operation, and escape of the steam from the interior of the cooker, said weights undertake a continuous rotation which creates an almost continuous surface in the upper edge of the top weight, upon which projections provided in the head are supported, thus preventing the weights from escaping. Therefore, during operation of the valve, projections provided in the head prevent the weights from escaping.
Another feature of conventional valves is their construction complexity requiring a large number of parts that make valves difficult to manufacture and to clean, at the same time making defects more likely to occur.
In order to solve this problem, the valve, of this invention comprises a small number of parts forming a whole that is easy to manufacture and use and at the same time does not shorten the useful life of the device.